A. Field of the Invention
The present invention relates to a method of manufacturing a color-converting filter that enables multi-color display. The color-converting filter can be used for display in image sensors, personal computers, word processors, televisions, facsimiles, audio equipment, video equipment, car navigation equipment, desk-top electronic calculators, telephones, mobile terminal equipment, industrial measuring equipment, and so on.
B. Description of the Related Art
In recent years, as one method of achieving multi-color or full-color display, studies have been carried out into a color conversion method in which color-converting colorants that absorb near ultraviolet light, blue light, blue/green light or white light, carry out wavelength distribution conversion and emit light in the visible region are used as filters (see Japanese Patent Application Laid-open Nos. 8-279394 and 8-286033.
In the case of using the color conversion method, the color of the light emitted by the light source is not limited to being white, and hence the degree of freedom of selection of the light source can be increased. For example, an organic EL light emitter that emits blue light can be used, and green and red light can be obtained through wavelength distribution conversion. The possibility has been investigated of constructing a full-color luminescent-type display for which a light source having improved efficiency can be used, including even a low-energy radiation such as near ultraviolet light or visible light (see Japanese Patent Application Laid-open No. 9-80434).
An important problem in terms of practical application to a color display is providing a color-converting filter that enables detailed color display, is stable in terms of color fidelity and so on over a prolonged period, and also has high color conversion efficiency. However, if the concentration of the color-converting colorants is increased to increase the color conversion efficiency, then a drop in the efficiency due to so-called concentration quenching, and decomposition of the color-converting colorants over time and so on will occur. Hence the current state of affairs is that the desired color conversion efficiency is obtained by increasing the thickness of the color-converting layers containing the color-converting colorants. In order to prevent concentration quenching and decomposition of color-converting colorants, introduction of a bulky substituent onto the colorant nucleus has been studied (see Japanese Patent Application Laid-open Nos. 11-279426, 2000-44824 and 2001-164245. Addition of a quencher has been studied as a means of preventing decomposition of color-converting colorants (see Patent Japanese Patent Application Laid-open No. 2002-231450).
Other documents that relate to color-converting filters include Japanese Patent Application Laid-open Nos. 5-134112, 7-218717, 7-306311, 5-119306, 7-104114, 7-48424, 6-300910, 7-128519, 9-330793, 8-27934, and 5-36475 and Gekkan Display, 1997, Vol. 3, No. 7.
To increase the level of detail of a multi-color or full-color display that uses the color conversion method, it is necessary to carry out highly detailed patterning of the color-converting layers. However, when the width of each line in the pattern is smaller than the film thickness of the color-converting layers, the reproducibility of the pattern shape and deformation of the pattern during subsequent manufacturing steps become problems. In addition, when the patterning is carried out using ordinary photolithography, an application step, an exposure step carried out while aligning the mask, and a developing step are required for each color of the color-converting layers. For example, when a full-color display is to be obtained, at least red, green and blue color-converting layers are required, and hence the manufacturing process requires many steps, and is complex.
The present invention is directed to overcoming or at least reducing the effects of one or more of the problems set forth above.